IC 7300 Frequency stability using a GPS reference - anyone done this?

Discussion in 'General Technical Questions and Answers' started by KN4LGM, Sep 14, 2020.

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  1. KN4LGM

    KN4LGM Ham Member QRZ Page

    I would like to add a GPS reference to my 7300. Has anyone done this something similar?
     
  2. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    I have an IC-7300... I've yet to feel it's not stable. Not even remotely.

    What issues are you having exactly? Seems "rock solid" on my 7300

    If yours isn't stable, I'd be looking at things like power supply issues....

    Dave
    W7UUU
     
    W4NNF, W4KJG and KG5THG like this.
  3. KN4LGM

    KN4LGM Ham Member QRZ Page

    I am interested in the ARRL FMTs, no I have not noticed any wobble but I would like to add it purely for the FMTs. Also, the 9300(and/or 9700) has a 10 Mhz input so I thought it might be possible on the 7300.
     
    Last edited: Sep 14, 2020
  4. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    OH! Well that is most assuredly a higher standard! I get it now.

    The FMT's are no slouch - I used to think they were sort of "relegated to history" but I know it's still very much a big thing.

    Good luck in your quest - I'd be curious how the GPS would be injected etc. - assuming USB / virtual serial port?

    I'll be watching... cool stuff.

    Dave
    W7UUU
     
  5. W1VT

    W1VT Ham Member QRZ Page

    Last edited: Sep 14, 2020
  6. KN4LGM

    KN4LGM Ham Member QRZ Page

    Last edited: Sep 14, 2020
  7. W9WQA

    W9WQA Ham Member QRZ Page

    not grasping this...?
    following.
     
  8. G0GSR

    G0GSR Ham Member QRZ Page

    I haven't heard of anyone doing this, probably because its not necessary or worth the effort.

    I check my 7300 against my GPSDO every now and then.
    Last time, it was +7Hz at 70MHz so an insignificant error as the frequency is lowered.

    Frank
     
  9. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    Doable? Possibly. Worth it? I doubt.

    IC-7300 sports a Murata XTCHH oscillator for the FPGA, with +-1 PPM stability. After a initial calibration / frequency alignment in lab, the equipment should be rock stable in HF bands. As @G0GSR mentioned above, that would translate to +- 7 Hz deviation in the worst-case, highest band - 70 MHz band. If you're a 20 meter use? That translates to +- 1.4 Hz deviation.

    Feasibility:
    The tuning (blue arrow) is performed inside the FPGA:

    7300-frontend-a.png

    The FPGA is fed by a 41.344 MHz clock rate: (click to enlarge)

    7300-block-a.png

    So, you would have to essentially have your GPSDO output this clock rate, yank off the existing clock, properly buffer and then feed it to the FPGA.

    Remember, if you lose sync/clock, it will probably cause a number of other problems of the radio, as the FPGA controls a number of functions on the radio.

    Again; worth it? I doubt it.

    - RF.
     
    Last edited: Sep 14, 2020
  10. KN4LGM

    KN4LGM Ham Member QRZ Page

    The person who won the last FTM was only of by a 100th of a hz off, that is why I want to do it. However, I see what difficulties would come with replacing the existing clock, thanks.
     
    PY2RAF likes this.

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